#9: MOUNTING & PATINAS Name___________
To mount pieces to a base, flatten the bottom. Establish 1-3 points (usually 2) for mounting. Either: oWeld: TIG-weld ¼ inch x 20NC stainless steel nuts using a square and third hand, or gas weld in brass nuts. Some pieces may require SS or brass threaded rod to be welded to bottom point of piece. oTap: Instead of welding, holes may be tapped into bottom of piece. Establish points as above, and/or weld in tabs as necessary (these may be added in wax before casting). Determine size of thread, and use a square while drilling the correct size pilot hole: for example, use a #7 (or 13/64") drill-bit for making ¼ inch threads. Next, use a square to thread or 'tap' the hole. (Minimum of three full turns.) oCarefully transfer holes to base. Use appropriate bit to drill a clearance hole in base material (stone, wood, etc.) Typically a countersink is necessary on underside of base to accommodate the screw head
PATINA SAFETY: Good ventilation and/or chemical respirator, goggles, rubber gloves, apron. FIRST AID: For the below chemical recipes: Flush eyes for 15 min. Wash skin with soap. If swallowed: give 2 glasses of milk or water, induce vomiting.
Pickle Bath: ¼ cup of Citric Acid per gallon of tap water, or one quart Vinegar per gallon of tap water. (All following recipes require distilled or filtered water) Liver of Sulfur: 1-2 Tbs/quart. Apply hot or cold (as undercoat). Light brown-to-gray-to-charcoal. Ferric Nitrate: 1-2 Tbs/quart. Apply hot-to-very hot. Honey-to-caramel-to-brown-to-maroon. Cupric Nitrate: 1-2 Tbs/quart. Apply very hot. Blue (or green if lightly over-sprayed with Ferric). Titanium Dioxide Mix: 1-2 Tbs & 5 drops Nitric Acid/quart. Apply hot. Opaque white or light gray.
A) Prep: All phases of welding, chasing, sanding, mounting, de-burring, etc. must be completely finished. To remove the final casting scale, flux, investment, and to even out surfaces, bronzes may be treated with a variety of methods: brushed with wet pumice, sandblasted with #60 grit sand, rubbed with steel wool, sanded with scotch-brite pads or soaked in a "Pickle" for 1-8 hours, or until clean. These steps will also degrease the bronze of oils or fingerprints, as will Ammonia or Simple Green. B) Base: For most patinas, apply a base coat of cold Liver of Sulfur by soaking or spraying. Stop reaction by rinsing in tap water. Use scotch-brite pad to bring out highlights, leave recesses dark. C) Tools: Safety equipment, propane torch, turn-table, mixed chemicals in spray bottles, brushes, abrasives, paste wax and brush. Begin heating piece with torch as evenly as possible to approximately 200°F: rotate the piece often and focus heat near bottom, and on thicker areas. Test temp by spraying with distilled water: it should hit the surface and then completely steam off after about one second: D) Apply: Patina acids are gradually and evenly sprayed on. They may also be brushed onto specific areas. Distinct edges of color may be formed by masking or removing color through abrasion. For warm tones: Use Ferric Nitrate-the more chemical and the more heat, the darker it will become. For cool tones: Use Cupric Nitrate-piece must be very hot. Heat-flash to 'blossom.' Don't overheat! For opaque pastels: Use Titanium Mix-Heat evenly, apply. May be over-sprayed by other 3 colors. For dark overlay: Use Liver of Sulfur-may be lightly sprayed or brushed over the other 3 colors. E) Wax: When finished, brush on a thin, even coat of paste wax while still warm. Almost all patinas will darken when waxed. Warm tones are enhanced and cool tones are diminished, and so cools tones must be overdone. To change a waxed patina requires burning off the existing wax and starting over.